In the optical centering of spectacle lenses, a measuring brace is used for determining the centering data of an already anatomically adapted spectacle frame under use conditions. The centering data can be utilized for a measurement standard or reference as well as for detection of the frame forward inclination and head twist in video centering systems.
Video centering systems are known in the marketplace, such as the “System Video Infral” of the Carl Zeiss AG as well as a video centering system described in U.S. Pat. No. 6,659,609 which is incorporated herein by reference.
Conventionally, the optical spectacle glass centering takes place in that one views the test customer or test person with a video arrangement from a greater distance, for example, from a distance of 5 m and determines the relevant angles and dimensions in the video images and, from the relevant angles and dimensions, determines the centering data for the particular spectacle frame.
Measuring braces are known from the following publications: U.S. Pat. Nos. 6,659,609; 6,132,045; United States patent application publication 2002/0171806; German utility model registration 203 02 798 and German patent publications 100 20 005; 100 20 391; and 100 63 536. In addition, a measuring brace “Visu Point” of Ulev GmbH is known. The latter is seated loosely on the spectacle frame. The disadvantage here is that the measuring brace can fall from the spectacle frame with a slight movement of the test person. Furthermore, two rods are in the field of view of the test person which, in turn, is disturbing and can lead to measuring errors.